The invention relates to a directional indication instrument, in particular to a miniature directional indication drilling instrument capable of operation at elevated temperatures.
The oil and gas well drilling and survey fields as well as many other fields of industry require highly accurate and highly reliable measuring instruments and sensors. Measuring instruments and sensors used in the oil and gas well drilling and survey fields and many other industries, for example, aircraft equipment and military ordinance, must survive and operate accurately in extreme environmental conditions including, for example, extreme vibrations and impacts experienced at temperatures ranging from well below freezing to hundreds of degrees Centigrade. In these applications, measuring instruments and sensors are often tested for operation in broadband vibration environments as extreme as 20 g RMS; shock or impact environments in the range of 2,000 g""s; and temperature extremes ranging from xe2x88x9240 to +200 degrees Centigrade.
Well drilling and logging operations typically require that very expensive equipment and highly skilled workers operate in remote locations. This combination of factors results in operating costs that may run half a million dollars or more per day. Thus, an equipment failure which forces operations to shut-down may be very costly. To limit the costs associated with equipment failures, many operators keep spare parts on hand, including spare measuring instruments and sensors, even though the spare parts may be very expensive themselves. Such costly operations in such extreme environmental conditions demand sensors and measuring instruments which are compact, very rugged and highly reliable.
In the oil and gas industry, well drilling and logging environments have become even more severe as deposits are sought in ever deeper boreholes. The deeper the borehole the more extreme the temperature in which the drill string and drill string steering tools must operate. Directional drilling is often employed in which the boreholes contain changes in direction at various points along their depth. For example, the borehole may change from vertical to horizontal for short distances. Deep and angular boreholes often require the measuring instrument or sensor guiding the drill string to operate in very small spaces which may be one inch or less in diameter. Current directional instruments, however, are too large to operate effectively in these applications. For example, current instruments are typically 1.25 to 1.5 inch in diameter.
The directional drilling process uses sensing instruments incorporated into sensing systems which are placed downhole with the drilling bit to determine the location, direction and rate of change in position of the bit. Current direction sensor systems used in energy exploration are typically a complicated mix of sensors and electronics. Typical directional sensor systems are composed of separate acceleration and magnetic field sensors with discrete electronics providing input power and drive signals and sensing output signals. Typically, the separate sensors and electronic assemblies are mounted together on a single chassis.
Deeper boreholes require smaller diameter drill pipe and high temperature directional sensing systems which places a new and heavier burden on the current generation of directional sensing equipment. Size restrictions prohibit the use of current generation directional sensing equipment in many deep borehole drilling systems. The current large diameter directional sensing systems can not be placed in the drill stem bore without severely comprising other operations, such as drilling mud flow around the drilling and directional sensing systems. In deeper holes, the sharper turn radius required for horizontal drilling operations places additional length limitations on directional sensor systems. The long length of current directional sensor systems, typically on the order of 24 inches, limits the turn radius.
Use of electronics packages comprised of discrete electronic components to provide input power and drive signals and to sense output signals in current directional sensing systems limits the shock and vibration environments to which current instruments may be exposed. For example, lengthy wire bonds between discrete electronic components and printed wire boards combined with the inherent vibration sensitivity of printed wire boards limit both the operational and survival shock and vibration exposure limits of current instruments. Interconnect wiring between the various electronic packages and the sensors further limits the shock and vibration environments to which current instruments may be exposed.
Current directional instruments are typically limited to operate in temperature environments of +150 degrees Centigrade or less. Thus, current directional instruments are too temperature sensitive to operate effectively in environments in excess of +150 degrees Centigrade. For example, current instruments are too temperature sensitive to operate in deeper, hotter borehole applications. Differing coefficients of thermal expansion coefficients between components used in sensing instruments result in increased noise and other limitations. For example, differences in the thermal expansion coefficients of the package material and the acceleration sensor mechanism induces strain in accelerometers which reduces sensor accuracy and performance. Additionally, typical discrete packaged electronics breakdown during operation at high temperatures in excess of 150 degrees Centigrade.
Additionally, current directional sensing systems provide analog sensor signal voltages which require analog-to-digital conversion before signal transmission to the surface. In practice, analog-to-digital converter circuits in a drill string-mounted microprocessor may contribute large modeling errors.
The present invention overcomes the limitations of the prior art by providing a smaller directional indication sensor system of novel design capable of operating at elevated temperature. According to one aspect of the present invention, the present invention provides a directional indication sensor system which measures, for example, significantly less than 1 inch diameter as compared with the 1.25 to 1.50 inches diameter typical of current directional sensor systems and measures 7 inches in length as compared with 18 to 24 inches of typical directional sensor systems. Thus, a directional sensor system of the present invention provides angle measurement in applications from which current larger directional sensors are barred.
Additional advantages inherent in the smaller directional sensor system of the present invention include, for example, increased shock and vibration resistance. For example, the direction indication system of the present invention is more compact than current directional sensor systems, having a diameter under 1 inch and a length of 7 inches as compared with devices having diameters of 1.25 to 1.5 inch and a length of 18 to 24 inches. Thus, the system chassis has an inherently higher resonant frequency, or xe2x80x9cQ,xe2x80x9d than the chassis of current systems. Current directional indication systems are 5 to 10 times larger in volume than the device of the present invention. Thus, the directional indication system of the present invention has an increased shock and vibration resistance as a result of its inherently lower mass.
In part, the compactness of a directional indication system according to the present invention is due to the implementation of power supply and sensor drive and sense circuits in thick film or multi-chip module electronic assemblies. The thick film or multi-chip module electronics assemblies also contribute to the increased shock and vibration resistance of the directional sensor system of the present invention. For example, thick film or multi-chip module electronic assemblies are more compact and have smaller component size and shorter wire bonds than comparable circuits implemented using discrete components mounted on printed wiring boards. Additionally, the more compact multi-chip module electronics assembly or hybrid electronics assembly lends itself to more effective shock and vibration isolation mounting than is possible with current technology which uses discrete packaged integrated circuits on a printed wiring board. Sensor drive and sense functions may be implemented in one or more application specific integrated circuits and integrated with multi-chip module electronics assembly for even greater compactness. Such measures as implementing sensor drive and sense circuits in one or more multi-chip module electronics assemblies provides reduced noise and allows the control electronics to be co-located with respective sensors.
According to yet another aspect of the present invention, micro-electronics are utilized to improve the reliability of the sensor system""s electronic features, including the sensor system""s main electronics package. For example, the sensor system electronics package may be implemented in one or more hybrid electronics packages. In one example, power regulation, isolation, and filtering functions are implemented in one or more hybrid electronics packages. In another example, a digital controller chip provided on the main system electronics module controls the functions of the directional sensing system of the present invention. A main system electronics module provides serial digital output signals of the direction sensors which include three orthogonally mounted accelerometers, a three-axis magnetometer, a temperature signal output and a status word.
According to another aspect of the present invention, the present invention overcomes inherent temperature limitations of the prior art by providing a directional indication sensor system capable of operation at a higher temperature than current directional indication sensor systems. The present invention provides a directional indication sensor system capable of operation at elevated temperature, for example, 200 degrees Centigrade. The improved temperature capabilities provided by the present invention are another advantage derived by through use of power supply and drive and sense circuits in thick film or multi-chip module electronic assemblies and replacing discrete integrated circuits with application specific integrated circuits. Thus, the present invention provides a miniature directional indication sensor system which is capable of operating at elevated temperatures and within typical environmental shock and vibration regimes while providing the same or better performance as larger, temperature limited directional indication sensor systems.
According to still another aspect of the present invention, a miniature directional indication sensor system provides enhanced accuracy by providing serial digital output signals representative of direction and thermal sensors. Analog-to-digital conversion of sensor signals is implemented in a voltage-to-frequency converter circuit provided by the present invention. Furthermore, a miniature directional indication sensor system according to the present invention eliminates data lag between channels by providing simultaneous sampling of all the sensor channels.